ABSTRACTAn optimality criterion based on structural system reliability is presented for optimizing component sizes to satisfy a system reliability constraint. In this paper, optimality criteria and iterative formulas are developed. Some results in reliability optimization are presented and illustrated. An incremental loading approach is adopted for identifying failure modes and computing system reliability. For a number of illustrative examples, optimal designs were obtained within 3 to 5 iterations. With the aid of several examples, optimal weight characteristics of statically determinate and statically indeterminate structures are explained. These structures are loaded under both a single group of loads and different groups of loads.